Heat Pump-Based Water Harvesting Systems, And Methods Of Using Thereof

ABSTRACT

Provided herein are water harvesting systems, as well as methods of making and using such systems, for capturing water from surrounding air using a design that reduces overall energy costs of the systems and improve water harvesting cycle efficiency. The systems and methods use sorbent materials, such as metal-organic frameworks, to adsorb water from the air. The systems and methods desorb this water in the form of water vapor, and the water vapor is condensed into liquid water and collected. The liquid water is suitable for use as drinking water.

This United States Non-Provisional patent application claims the benefitof U.S. Provisional Patent Application No. 63/180,590, filed Apr. 27,2021, hereby incorporated by reference herein.

FIELD

The present disclosure generally relates to water harvesting, and morespecifically to a water harvester, and methods of making a waterharvester and methods of using a water harvester for harvesting waterfrom surrounding air.

BACKGROUND

Conventionally, the process of harvesting water from air with sorbentscomprises a water harvesting cycle including three energy-intensivestages: adsorption of water vapor from air to a sorbent, desorption ofwater vapor from the sorbent, and condensation of desorbed water vaporinto liquid water. For example, during the adsorption stage, humidenvironmental air may be blown across a desorbed (activated) sorbentbed. Molecules of water can diffuse through the porous interior of thesorbent bed and become adsorbed by the sorbent. The adsorption stage iscompleted when the sorbent bed becomes fully saturated with water.Following the adsorption stage, a desorption stage can be initiated bydirectly or indirectly heating up the sorbent bed to release watervapor. The desorption stage is completed when the sorbent bed becomesdesaturated of water. During the condensation stage, water vaporgenerated during the desorption stage can be directed to a condensationchamber, where the water vapor cools and condenses into liquid water.Through repetitive cycles of adsorption, desorption and condensation,sorbent-based water harvesting can provide a method to produce waterfrom air.

Generally, there are two heating methods to release water from thesaturated sorbent bed: first, direct heating that involves heat transferfrom a heat source directly to the surface of the sorbent bed supportstructure, the sorbent bed, or the sorbent; and second, an indirectheating that involves heating the air surrounding the sorbent bedsupport structure, the sorbent bed, or the sorbent. Both direct heatingand indirect heating can be achieved with resistive heating. Desorptiontypically requires significant energy, including a latent heat portionrelated to the desorption energy to change water associated with thesorbent to water vapor, and a sensible energy portion related to heatingone or more of the sorbent bed support structure, the sorbent bed, orthe sorbent. Potentially, the energy spent on desorption can berecovered during the condensation stage and then reintroduced into thesystem for desorption. Generally, resistive heating does not provide forrecovery of energy spent on desorption.

What is desired in the art are commercially viable water harvestingsystems for harvesting water from surrounding air that by comparison toconventional water harvesting systems reduces energy costs and/orimproves efficiency in water production during the water harvestingcycle.

BRIEF SUMMARY

Provided herein are heat pump-based water harvesting systems that canreduce overall energy costs in the water harvesting cycle and/orimproves efficiency in water production during the water harvestingcycle.

A broad object of embodiments of the invention can be to provide anatmospheric water harvesting system, comprising one or more of: aheat-pump system; an adsorption unit; a desorption chamber; a transfermechanism; and a condensation chamber. In particular embodiments, theheat-pump system can comprise one or more of: a compressor, an expansionvalve, and a heat exchanger, wherein the heat exchanger has a hot side(typically a “condenser”) and a cold side (typically an “evaporator”).In particular embodiments, the adsorption unit comprises at least onesorbent module, wherein the at least sorbent module contains one or moresorbents, and the adsorption unit can, but need not necessarily, bephysically separated from the heat-pump system. In some embodiments, thedesorption chamber can be connected to or positioned in close proximityto the hot side of the heat exchanger, and can be configured to operateat an average desorption temperature. In particular embodiments, thetransfer mechanism can be configured to (i) transfer a sorbent module atleast partially saturated with water from the adsorption unit into thedesorption chamber, and (ii) transfer the sorbent module at leastpartially desorbed in the desorption chamber back to the adsorptionunit. In particular embodiments, the condensation chamber can encompassor be positioned in close proximity to the cold side of the heatexchanger, and can be configured to operate at an average condensationtemperature. In particular variations of the foregoing, the waterharvesting system can be configured to operate at an average desorptiontemperature and the average condensation temperature for the system to(i) achieve the lowest energy per liter of water produced with the oneor more sorbents, or (ii) maintain a desorption temperature high enoughto sustain a target rate of desorption, and combinations thereof.

Another broad object of the invention can be a method of harvestingwater from surrounding air, including using any one or combinations ofthe atmospheric water harvesting systems described herein. In particularembodiments, the method comprises: a) drawing surrounding air into atleast one sorbent module which may be positioned in the adsorption unit,wherein the at least one sorbent module adsorbs water from thesurrounding air; b) once the at least one sorbent module becomes atleast partially saturated or saturated to a target level of water and/orrate of adsorption, transferring the at least one sorbent module to thedesorption chamber, which may achieved using the transfer mechanism tomove the sorbent module from the adsorption unit to the desorptionchamber; c) blowing air or an air/water mixture across the hot side ofthe heat pump through the at least one sorbent module positioned in thedesorption chamber to facilitate water desorption; d) transferring hotwater vapor from the desorption chamber to the cold side of the heatpump, which may be coordinated with the desorption chamber achieving atarget water concentration; e) optionally repeating steps c) and d)until the at least one sorbent module in the desorption chamber becomesdepleted of adsorbed water; and f) transferring the at least one sorbentmodule from the desorption chamber after desorption, which may becoordinated using the transfer mechanism to move the sorbent module fromthe desorption chamber to the adsorption unit. In particular variationsof the foregoing, the method can be performed at an average desorptiontemperature or the average condensation temperature for the waterharvesting system, or combinations thereof, to (i) achieve the lowestenergy per liter of water produced with the one or more sorbents, or(ii) maintain a desorption temperature high enough to sustain a targetrate of desorption, and combinations thereof.

DESCRIPTION OF THE FIGURES

The present application can be best understood by reference to thefollowing description taken in conjunction with the accompanying figuresincluded in the specification.

FIG. 1 depicts a schematic of an exemplary heat pump-based waterharvesting system.

FIG. 2A depicts an exemplary heat pump-based water harvesting systemthat includes a rotating carousel configured to continuously move fullysaturated MOF modules into the desorption chamber of thedesorption/condensation unit for desorption.

FIG. 2B depicts another exemplary heat pump-based water harvestingsystem that includes a multi-axis robotic arm configured to switch theMOF modules between the adsorption rack and the desorption chamber.

FIG. 3 depicts an exemplary schematic for thermal coupling between the“condenser” hot-side heat exchanger and the MOF module in a desorptionchamber.

FIG. 4 depicts an exemplary schematic for water vapor condensation andliquid water collection.

FIG. 5 depicts parts of an exemplary heat pump-based water harvestingsystem in which the temperature, humidity, and velocity of thecirculating air values are measured.

DETAILED DESCRIPTION

The following description sets forth illustrative examples of heatpump-based water harvesting systems (1), methods of making heatpump-based water harvesting systems (also referred to as the “system”),and methods of using heat pump-based water harvesting systems. It shouldbe recognized, however, that the examples of heat pump-based waterharvesting system (1) provided by the description are not intended tolimit the breadth or scope of the description, but instead to provideexamples sufficient for a person of ordinary skill in the art to makeand use the full breadth and scope of the invention.

Now with primary reference to FIGS. 1 through 5 , provided is asorbent-based water harvesting system (1) including a heat pump (2) toeffectively recover condensation energy and use it for desorption. Incertain aspects, provided is a method of using any of the sorbent-basedwater harvesting systems (1) described herein. In some embodiments, thesystem (1) includes an adsorption unit (3), such as an adsorption rack,that that holds one or more sorbent modules (4) containing at least onesorbent material (5). Air (6) can flow across one or more sorbentmodules (4), leading to adsorption of water (7) from the surrounding air(6) by the sorbent material (5) therein. The system (1) includes atransfer mechanism (8), which in particular embodiments can be acarousel (8 a) (as shown in the example of FIG. 2A) or can be a roboticarm (8 b) (as shown in the example of FIG. 2B). Once one or more of thesorbent modules (4) reach a target level and/or a target rate ofadsorption, the transfer mechanism (8) can move the one or more sorbentmodules (4) containing adsorbed water from the adsorption unit (3) to adesorption chamber (9) of the system (1). In some embodiments, thedesorption chamber (9) includes a recirculation fan (10) that blows airor an air/water mixture (11) across a hot side (12) of the heat pump (2)through the one or more sorbent modules (4) to facilitate desorption.Once a target water concentration is achieved in the desorption chamber(9), in particular embodiments, the system (1) can turn on adesorption-condenser recirculation fan (13) present in the desorptionchamber (9) to transfer hot water vapor (14) from the desorption chamber(9) to a cold side (15) of the heat pump (2) encompassed in, orpositioned in closer proximity to, a condensation chamber (16). In somevariations, the optimal average desorption temperature and/or averagecondensation temperature for the system (1) can be configured to achievethe lowest energy per liter of water (7) produced with the sorbentmaterial (5) and can keep the desorption temperature high enough tosustain a target desorption rate. Upon depletion of the sorbent module(4), the transfer mechanism (8) can remove the one or more sorbentmodules (4) from the desorption chamber (9) and places the one or moresorbent modules (4) back into the adsorption unit (3). Embodiments ofthe sorbent-based water harvesting system (1) can achieve increasedwater adsorption, as well as continuous desorption and condensation atelevated temperatures.

In particular embodiments, as depicted in FIG. 2A, the example system(1) utilizes a carousel (8 a) which rotates one or more sorbentmodule(s) (4). While one or more sorbent modules (4) are being desorbed,the remaining sorbent modules (4) can be in the adsorption stage beingexposed to humid environmental air (6). In particular embodiments, asdepicted in FIG. 2B, utilized a robotic arm (8 b) to transfer the one ormore sorbent modules (4) from an adsorption rack (17) to the desorptionchamber (9). Again, with reference to FIG. 1 , in particularembodiments, the heat-pump (2) includes a heat exchanger (18), which hasa hot side (12) and a cold side (15). In some variations, the heat-pump(2) may include a compressor (19), an expansion valve (20), a main“condenser” or hot-side heat exchanger (21), a secondary hot-side heatexchanger (22), an “evaporator” or cold-side heat exchanger (23), andother control components designed to operate at elevated temperatures.For example, in particular embodiments, the “condenser” or hot side ofthe heat exchanger (21) can be set to operate at temperatures in therange of about 90° C. to about 160° C., and the “evaporator” orcold-side heat exchanger (23) can be set to operate at temperatures inthe range of about 40° C. to about 95° C.

Again, with reference to FIG. 1 , the “condenser” or hot side of theheat exchanger (21) in the desorption chamber (9) and the “evaporator”or cold-side heat exchanger (23) in the condensation chamber (16) can berespectively coupled to a heat sink(s) (24 a, 24 b) to providesubstantially constant or constant temperature operation when thesorbent modules (4) move in and out of the desorption chamber (9). Theheat sink(s) (24 a, 24 b) can be a metal block or any other material ofhigh thermal mass in both the desorption chamber (9) and condensationchambers (16). It can also be liquid water (7) in the condensationchamber (16).

The performance of a heat pump (2) in the system (1) can generally bemodelled by the following equations:

$\begin{matrix}{W = \frac{Q_{c}}{COP}} & (1)\end{matrix}$ and $\begin{matrix}{{COP} = {f\frac{T_{c}}{T_{h} - T_{c}}}} & (2)\end{matrix}$

where W is the work input by the compressor (19), Q_(c) is the energyextracted from the cold-side heat exchanger (23), COP is the coefficientof performance, T_(h) is the temperature of the hot-side heat exchanger(21), T_(c) is the temperature of the cold-side heat exchanger (23), andf is an empirical coefficient based on practical design of the system(1). In some variations, f is between about 0.4 to about 0.6. LowT_(h)−T_(c) and high T_(c) values typically lead to a moreenergy-efficient design of the heat pump (2).

In certain embodiments, the system (1) and methods of using the system(1) can be devised to ensure effective thermal coupling between thehot-side heat exchanger (21) and the desorbing sorbent module(s) (4).Hot water vapor (14) generated during desorption can be directed to thecondensation chamber (16) which contains the “evaporator” or cold-sideheat exchanger (23) where the vapor can be condensed into water (6).Liquid water (6) can then be collected in a water tank (25). Theresidual saturated and relatively cold water vapor (7 b) can berecirculated back into the desorption chamber (9) to avoid excessivewater loss in the environment.

In some variations, the system (1) can further include a computer (26)coupled to one or more ambient air temperature sensors (27) and/orambient air humidity sensors (28) located outside of the desorptionchamber (9) and condensation chamber (16) adapted to or configured tomeasure ambient air temperature and/or ambient air humidity of theenvironment surrounding the system (1). The computer (26) can berespectively coupled to one or more temperature sensors (29 a, 29 b)and/or one or more humidity sensors (30 a, 30 b) and/or one or moreairflow sensors (31 a, 31 b) that can be respectively located inside thedesorption chamber (9) and/or the condensation chamber (16) to measurerespective desorption chamber temperature and/or humidity, and/orcondensation chamber temperature and/or humidity. The temperature and/orhumidity measurements based on readings from the desorption chamber andcondensation chamber sensors (29 a, 29 b, 30 a, 30 b) and theenvironment temperature and/or humidity measurements based on readingsfrom the ambient temperature and humidity sensors (27, 28) can be usedunder the control of the computer (26) implementing a water harvestingalgorithm (31) to adjust operating parameters of the system (1), forexample, to modify performance of the system (1) in terms of energy use,water production, and operation of the heat-pump.

Any suitable sorbent material (5) can be used in embodiments of thesystem (1) and methods described herein. In particular embodiments, thesorbent material (5) can include one or more metal-organic frameworks(“MOFs”). Generally, MOFs offer unique characteristics that aredesirable for harvesting water (7) from air (6). See e.g., H. Furukawaet al., Water Adsorption in Porous Metal-Organic Frameworks and RelatedMaterials, J. Am. Chem. Soc. 2014, 136, 11, 4369-4381. MOFs may becharacterized by high water uptake and step-like characteristics forwater uptake versus relative humidity (“RH”). In some variations,suitable sorbent materials (5), including MOFs, have such an isothermstep, which can be tailored to various climates. See e.g., WO2020112899.The isotherm step is typically a weak function of temperature due tohydrogen binding between the interior of the MOF pore and the watermolecules. The step isotherm enables water capture and release by MOF ina very narrow range of relative humidity (about 3 to about 5% of RH).

In some variations, the MOF is: MOF-303: Al(OH)(HPDC), where HPDC is1H-pyrazole-3,5-dicarboxylate; CAU-10: Al(OH)(IPA), where IPA isisophthalate; MOF-801: Zr₆O₄(OH)₄(fumarate)₆; MOF-841:Zr₆O₄(OH)₄(MTB)₆(HCOO)₄(H₂O)₂; Aluminum Fumarate: Al(OH)(fumarate);MIL-160: Al(OH)(FDA), where FDA is 2,5-furandicarboxylate; MIL-53:Al(OH)(TPA), where TPA is terephthalate; or Aluminum Phosphate:AlPO4-LTA. In some variations, the MOFs have pore sizes in the range ofabout 0.5 nm to about 1 nm, or between about 0.7 nm to about 0.9 nm. Incertain variations, the MOFs have a hydrophilic pore structure. Incertain variations, the MOFs have a hydrophilic pore structurecomprising acid and/or amine functional groups. In certain variations,the MOFs have one-dimensional channels that allow for reversible wateradsorption. Any combinations of the MOFs described herein, or otherMOFs, or sorbents capable of water adsorption/desorption may also beused. In some embodiments, the MOF can be mixed with a binder to improveits properties for adhesion to a substrate or support.

In other variations, other sorbents (5) having high water uptakeabilities as well as the isotherm step described above may be used inthe systems and methods described herein. Other suitable sorbents (5)may include, for example, certain molecular sieves (as one example,SAPO-34 a micropore zeolite, CAS No. 1318-02-1) and certain zeoliteshaving the properties described above.

Rate of water desorption in the sorbent materials (5) (including theabove-described MOFs) and saturated vapor pressure in air valuesincrease exponentially with temperature. The specific desorption energy,on the other hand, decreases with temperature. These three factors allfavor a design of the desorption process at elevated temperatures.However, higher desorption temperature incurs a higher sensible heatpenalty from the sorbent material (5), water (7) inside the sorbentmaterial (5), support structure, recirculating air (7), and water vapor.The condensation temperature needs to be below the dew point of thedesorbed hot water vapor (14). More water (7) can be condensed in asingle pass through the cold-side heat exchanger (23) with lowercondensation temperature, but the heat-pump COP value becomes lower withincrease in T_(h)−T_(c) and decrease in T_(c). Consequently, desorptionand condensation temperatures for the water harvesting system (1) can beadjusted to achieve the lowest energy per liter of water produced with agiven sorbent material (5).

Again, with primary reference to FIG. 2A, another example of the system(1) is depicted in which a rotating carousel (8 a) continuously movesfully saturated MOF containing sorbent module(s) (4) into a desorptionchamber (9) for desorption. Once a MOF sorbent module (4) moves into thedesorption chamber (9), it is heated-up to release water (7) as hotwater vapor (14). Simultaneously, the other MOF sorbent modules (4) canbe exposed to humid air (6) blown across them to initiate adsorption.Upon completed desorption, a motor (32) with positioning control rotatesthe carousel (8 a) to move the desorbed sorbent module or MOF sorbentmodule (4). out of the desorption chamber (9) and allowing a saturatedMOF sorbent module (4) to enter the desorption chamber (9).

With reference to FIG. 2B, another example of the system (1) is depictedin which a multi-axis robotic arm (8 b) (or other automated mechanism)handles switching of the MOF sorbent modules (4) between the adsorptionrack (17) and the desorption chamber (9). As soon as the MOF sorbentmodule (4) is sufficiently desorbed in the desorption chamber (9), itcan be removed by the robot arm (8 b) and placed back into theadsorption rack (17). A new fully adsorbed MOF sorbent module (4) can bepicked up and placed by the robotic arm (8 b) into the desorptionchamber (9). A computer and water harvesting algorithm (31) can be usedto track desorption and adsorption status of each module.

Now, with primary reference to FIG. 3 , a schematic diagram illustratesa thermal coupling between the “condenser” hot-side heat exchanger (21)and the MOF sorbent module (4) in a desorption chamber (9). Thedesorption chamber (9) is thermally isolated from the environment withinsulated walls (32). A recirculation fan (10) blows air (6) across thehot-side heat exchanger (21) to raise the temperature when asufficiently adsorbed MOF sorbent module(s) (4) is placed into thedesorption chamber (9). This air (6) heated by being blown across thehot-side heat exchanger (21) can then be blown across the MOF sorbentmodule(s)(4) to raise the temperature of the MOF sorbent module (4) torelease the adsorbed water (7). A portion of the hot water vapor (14)released from the MOF sorbent module (4) can then be circulated by therecirculation fan (10) back to the hot-side main heat exchanger (21) tocontinue raising the at least one MOF sorbent material (5) temperatureto the desired operating desorption temperature. A portion of the hotwater vapor (14) from the MOF sorbent module (4) can be directed to thecondensation chamber (16) for condensation. Pending on vapor conditions(RH and temperature values) at the exit of the MOF sorbent module (4),the re-circulating and desorption rates can be adjusted withvariable-speed recirculation fan (10) airflow using a pre-determinedalgorithm (31). The goals are to achieve a constant energy load of theheat exchangers and to maintain a high moisture content of the watervapor for more efficient condensation yield. Thermal coupling betweenthe hot-side heat exchanger (21) and the MOF sorbent module (4) can alsobe improved by physical contact of the heat exchanger and the MOFsorbent module (4).

It should be understood that while FIGS. 2A, 2B and 3 illustrateparticular embodiments of MOF sorbent modules (4) in the system (1),other suitable sorbent modules (4) may be used in other variations ofthe systems (1) described herein.

Now, with primary reference to FIG. 4 , which depicts an illustrativeschematic for the water vapor (14) condensation and liquid water (7)collection. In such embodiment, the condensation chamber (16) can beenclosed in a thermally insulated wall (32) (or other manner ofcondensation chamber insulation). Hot water vapor (14) can be piped infrom the desorption chamber (9) and passed through the “evaporator”cold-side heat exchanger (23) allowing the hot water vapor (14) to cooland water (7) to condense upon reaching the dew point. The exhaustcarries cooler air/water mixture (11) back into the desorption chamber(9). A heat sink (24 b) can be thermally coupled to the cold-side heatexchanger (23) to maintain the desired operating temperature for watercondensation. Liquid water (7) can drip down from the fins of thecold-side heat exchanger (23) and can be collected in the watercollection tank (25) below. A desorption-condenser recirculation fan(13) can be used to control and recirculate hot-water vapor (14) and theexhaust cooler an air/water mixture (11) between the desorption chamber(9) and condensation chamber(s) (16).

Now, with primary reference to FIG. 5 which depicts components of anillustrative example of a particular embodiment of the system (1) wherethe temperature, humidity, and velocity of the circulating air valuescan be measured, as above described. Temperature of the hot-side heatexchanger (21) and cold-side heat exchanger (23) can also be measured.Based on these measured values, the computer (26) by execution of thewater harvesting algorithm (31) can assess the energy loads for eachheat exchanger (21, 22, 23). In some variations, the computer (26) inthe system (1) may be programmed to adjust the air flow rates bychanging the fan speed of the recirculating fans (10, 13) to maintainnearly constant energy loads for each heat exchanger (21, 22, or 23)included in the system (1) and to achieve the desired temperature forthe desorption and condensation processes.

Heat pump energy balance can be obtained between the power input of thecompressor, {dot over (W)}, the energy load of the cold-side heatexchanger, {dot over (Q)}_(c), and the energy loads of the hot-side heatexchangers, which are denoted by {dot over (Q)}_(hm) and {dot over(Q)}_(hs) separately for the main and the secondary heat exchangers canbe expressed as:

{dot over (W)}=({dot over (Q)} _(hm) +{dot over (Q)} _(hs))−{dot over(Q)} _(c)  (3)

See R. Sonntag and C. V. Wylen, Introduction to Thermodynamics Classicaland Statistical, 2^(nd) ed., John Wylie and Sons, 1982.

The compressor work input is constant based on the compressor design andthe operating conditions. In some variations, to recycle the majority ofthe recovered condensation heat for desorption, the system is configuredto set the following:

{dot over (Q)} _(hm) ={dot over (Q)} _(c)  (4)

and

{dot over (Q)} _(hs) ={dot over (W)}  (5)

Thus, the energy load of the hot-side heat exchanger (21) equals to thatof the cold-side heat exchanger (23). Some power input can be dissipatedby the secondary hot-side heat exchanger (22) to the environment.

The hot-side heat exchanger (21) configuration may be modeled by takinginto account energy “gain” due to incoming and outgoing airflow, whichshould be equal to the energy dissipated by the hot-side heat exchanger.

{dot over (Q)} _(hm) ={dot over (m)} _(b) C _(pb) T _(b) −{dot over (m)}_(a) C _(pa) T _(a)  (6)

where {dot over (m)}_(b) is the air/water vapor mixture mass flow rate,C_(pb) the specific heat capacity, and T_(b) the temperature at locationb; {dot over (m)}_(a) is the air/water vapor mixture mass flow rate,C_(pa) the specific heat capacity, and T_(a) the temperature at locationa. T_(b) should be approximately equal to T_(h), which is the operatingtemperature of the hot-side heat exchanger (21) with a targeted heatexchanger design. The mass flow rate can be estimated using the airdensity, air velocity and cross-sectional area of the heat exchanger.Initially, when the fully adsorbed sorbent module (4) (e.g., MOF sorbentmodule) is moved into the desorption chamber (9) for desorption, T_(a)is low but quickly heats up during the desorption process. The system(1) increases the desorption recirculation fan speed (10) according tothe equation (6) to maintain constant {dot over (Q)}_(hm).

The energy balance for the secondary hot-side heat exchanger (22) can beexpressed as follows:

{dot over (Q)} _(hs) ={dot over (W)}=h _(s) A _(s)(T _(h) −T _(f))  (7)

where h_(s) is the heat transfer coefficient of the secondary hot-sideheat exchanger (22) which is a function of heat transfer geometry andair flow, A_(s) area of the fins of the heat exchanger, and T_(f) theenvironment temperature. The system (1) adjusts the rate of the airflowacross the secondary hot-side heat exchanger (22) to maintain a constantenergy dissipation rate as the environment temperature changes.

Both the sensible heat and the latent heat portions of the energy loadat the cold-side heat exchanger need to be considered for thecondensation process.

$\begin{matrix}{{\overset{.}{Q}}_{c} = {{{\overset{.}{m}}_{d}C_{pd}T_{d}} - {{\overset{.}{m}}_{e}C_{pe}T_{e}} + {H_{f{\mathcal{g}}}\left( {{\frac{{\overset{.}{m}}_{d}}{\rho_{d}}\Phi_{d}} - {\frac{{\overset{.}{m}}_{e}}{\rho_{e}}\Phi_{e}}} \right)}}} & (8)\end{matrix}$

where {dot over (m)}_(d) is the air/water vapor mixture mass flow rate,C_(pd) the specific heat capacity, T_(d) the temperature, ρ_(d) the airdensity, and Φ_(d) the absolute humidity at location d; {dot over(m)}_(e) is the air/water vapor mixture mass flow rate, C_(pe) thespecific heat capacity, T_(e) the temperature, ρ_(e) the air density,and Φ_(e) the absolute humidity at location e and H_(fg) is the latentheat of water at the condensation temperature. T_(e) should beapproximately equal to the cold-side heat exchanger temperature with thetargeted heat exchanger design.

In some variations, the system (1) adjusts the desorption-condensationrecirculation fan (13) speed to maintain a constant energy load for thecold-side heat exchanger (23) as temperature and humidity values of theincoming and outcoming air/water vapor mixture changes.

Again, with primary reference to FIG. 5 , a method of using a particularembodiment of the invention can comprise one or more of: drawingsurrounding air (6) into at least one sorbent module (4) positioned inan adsorption unit (3), wherein at least one sorbent module (4) adsorbswater (7) from the surrounding air (6); once the at least one sorbentmodule (4) is saturated to a target level of water (7) and/or rate ofadsorption, transferring the at least one sorbent module (4) from theadsorption unit (3) to a desorption chamber (9) using a transfermechanism (8, 8 a, 8 b); moving an air/water mixture (11) across a hotside (12) of a heat pump (2) through at least one sorbent module (4)positioned in the desorption chamber (9) to facilitate water desorption;optionally repeating the method until the at least one sorbent module(4) in the desorption chamber (9) is depleted of adsorbed water; andtransferring the at least one sorbent module in the desorption chamberafter desorption to the adsorption unit using the transfer mechanism.

In particular embodiments, the method can further comprise performingthe method at an average desorption temperature and the averagecondensation temperature for the system to (i) achieve the lowest energyper liter of water produced with the one or more sorbents, and (ii)maintain a desorption temperature high enough to sustain a target rateof desorption.

In particular embodiments the method can further comprise one or moreof: transferring hot water vapor (14) from the desorption chamber (9) toa cold side (15) of the heat pump (2); condensing water from said hotwater vapor; and collecting water condensed from said hot water vapor.

EXAMPLES

The presently disclosed subject matter will be better understood byreference to the following Examples, which are provided as illustrativeexamples of embodiments of the invention, and not by way of limitation.

Example 1 Desorption and Condensation Temperatures

The example describes desorption and condensation temperatures used in awater harvesting system (1). The model used an iterative procedure.First, the model set the initial desorption and condensationtemperatures of the system (1). Based on the isotherm step of thesorbent, the absolute humidity in the desorption chamber was known atthe given desorption temperature. The condensation yield can becalculated for the given condensation temperature, if the relativehumidity and temperature of the water vapor in the desorption chamber isknown. The efficiency of the heat pump (2) can be computed with Equation2 assuming f=0.6 and in turn the work input is calculated usingEquation 1. In addition to the desorption and condensation energy, themodel further considered the sensible heat value required to heat up thesorbent, water inside sorbent, air, and vapor. The model also took intoaccount the temperature of the recycled water vapor (11) and thespecified total water harvesting yield of the system. Thus, the systemenergy consumption per liter of harvested water (7) was approximated asa function of the desorption and condensation temperatures with a givenMOF sorbent material (5). Operating conditions can be obtained byvarying the two variables (desorption and condensation temperatures).See Table 1 below.

TABLE 1 Isotherm step Desorption Condensation MOF @25° C. TemperatureTemperature Type (RH %) (° C.) (° C.) Arid 20 136 90 Moderate 40 117 91Humid 60 107 92

Table 1 shows the desorption and condensation temperatures for threetypes of MOF sorbent materials (5). The water harvester which containsan Arid-type MOF with an isotherm step of 20% of relative humidity (RH)at 25° C. can operate at the desorption temperature of about 136° C. andthe condensation temperature of about 90° C. Moderate MOF with anisotherm step of RH 40% requires desorption and condensationtemperatures of about 117° C. and about 91° C., respectively; while aHumid MOF with an isotherm step of RH 60% requires desorption andcondensation temperatures at about 107° C. and about 92° C.,respectively.

Table 1 indicates that utilization of a high-temperature heat pump (2)may be required to achieve the lowest energy consumption per liter ofharvester water (7) given that the high-temperature heat pump operatesat about 90° C. to about 160° C. for the hot-side heat exchanger (21)and about 40° C. to about 95° C. for the cold-side heat exchanger (23).

As can be easily understood from the foregoing, the basic concepts ofthe present invention may be embodied in a variety of ways. Theinvention involves numerous and varied embodiments of a water harvestingsystem (1) and methods for making and using such water harvesting systemincluding the best mode.

As such, the particular embodiments or elements of the inventiondisclosed by the description or shown in the figures or tablesaccompanying this application are not intended to be limiting, butrather exemplary of the numerous and varied embodiments genericallyencompassed by the invention or equivalents encompassed with respect toany particular element thereof. In addition, the specific description ofa single embodiment or element of the invention may not explicitlydescribe all embodiments or elements possible; many alternatives areimplicitly disclosed by the description and figures.

It should be understood that each element of an apparatus or each stepof a method may be described by an apparatus term or method term. Suchterms can be substituted where desired to make explicit the implicitlybroad coverage to which this invention is entitled. As but one example,it should be understood that all steps of a method may be disclosed asan action, a means for taking that action, or as an element which causesthat action. Similarly, each element of an apparatus may be disclosed asthe physical element or the action which that physical elementfacilitates. As but one example, the disclosure of a “water harvester”should be understood to encompass disclosure of the act of “waterharvesting”—whether explicitly discussed or not—and, conversely, werethere is a disclosure of the act of “water harvesting”, such adisclosure should be understood to encompass disclosure of a “waterharvester” and even a “means for water harvesting”. Such alternativeterms for each element or step are to be understood to be explicitlyincluded in the description.

In addition, as to each term used it should be understood that unlessits utilization in this application is inconsistent with suchinterpretation, common dictionary definitions should be understood to beincluded in the description for each term as contained in the RandomHouse Webster's Unabridged Dictionary, second edition, each definitionhereby incorporated by reference.

All numeric values herein are assumed to be modified by the term“about”, whether or not explicitly indicated. For the purposes of thepresent invention, ranges may be expressed as from “about” oneparticular value to “about” another particular value. When such a rangeis expressed, another embodiment includes from the one particular valueto the other particular value. The recitation of numerical ranges byendpoints includes all the numeric values subsumed within that range. Anumerical range of one to five includes for example the numeric values1, 1.5, 2, 2.75, 3, 3.80, 4, 5, and so forth. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint. When a value is expressed as an approximation by use of theantecedent “about,” it will be understood that the particular valueforms another embodiment. The term “about” generally refers to a rangeof numeric values that one of skill in the art would consider equivalentto the recited numeric value or having the same function or result.Similarly, the antecedent “substantially” means largely, but not wholly,the same form, manner or degree and the particular element will have arange of configurations as a person of ordinary skill in the art wouldconsider as having the same function or result. When a particularelement is expressed as an approximation by use of the antecedent“substantially,” it will be understood that the particular element formsanother embodiment.

Moreover, for the purposes of the present invention, the term “a” or“an” entity refers to one or more of that entity unless otherwiselimited. As such, the terms “a” or “an”, “one or more” and “at leastone” can be used interchangeably herein.

Further, for the purposes of the present invention, the term “coupled”or derivatives thereof can mean indirectly coupled, coupled, directlycoupled, connected, directly connected, or integrated with, dependingupon the embodiment.

Additionally, for the purposes of the present invention, the term“integrated” when referring to two or more components means that thecomponents (i) can be united to provide a one-piece construct, amonolithic construct, or a unified whole, or (ii) can be formed as aone-piece construct, a monolithic construct, or a unified whole. Saidanother way, the components can be integrally formed, meaning connectedtogether so as to make up a single complete piece or unit, or so as towork together as a single complete piece or unit, and so as to beincapable of being easily dismantled without destroying the integrity ofthe piece or unit.

Thus, the applicant(s) should be understood to claim at least: i) eachof the water harvesters herein disclosed and described, ii) the relatedmethods disclosed and described, iii) similar, equivalent, and evenimplicit variations of each of these devices and methods, iv) thosealternative embodiments which accomplish each of the functions shown,disclosed, or described, v) those alternative designs and methods whichaccomplish each of the functions shown as are implicit to accomplishthat which is disclosed and described, vi) each feature, component, andstep shown as separate and independent inventions, vii) the applicationsenhanced by the various systems or components disclosed, viii) theresulting products produced by such systems or components, ix) methodsand apparatuses substantially as described hereinbefore and withreference to any of the accompanying examples, x) the variouscombinations and permutations of each of the previous elementsdisclosed.

The background section of this patent application, if any, provides astatement of the field of endeavor to which the invention pertains. Thissection may also incorporate or contain paraphrasing of certain UnitedStates patents, patent applications, publications, or subject matter ofthe claimed invention useful in relating information, problems, orconcerns about the state of technology to which the invention is drawntoward. It is not intended that any United States patent, patentapplication, publication, statement or other information cited orincorporated herein be interpreted, construed or deemed to be admittedas prior art with respect to the invention.

The claims set forth in this specification, if any, are herebyincorporated by reference as part of this description of the invention,and the applicant expressly reserves the right to use all of or aportion of such incorporated content of such claims as additionaldescription to support any of or all of the claims or any element orcomponent thereof, and the applicant further expressly reserves theright to move any portion of or all of the incorporated content of suchclaims or any element or component thereof from the description into theclaims or vice-versa as necessary to define the matter for whichprotection is sought by this application or by any subsequentapplication or continuation, division, or continuation-in-partapplication thereof, or to obtain any benefit of, reduction in feespursuant to, or to comply with the patent laws, rules, or regulations ofany country or treaty, and such content incorporated by reference shallsurvive during the entire pendency of this application including anysubsequent continuation, division, or continuation-in-part applicationthereof or any reissue or extension thereon. The elements following anopen transitional phrase such as “comprising” may in the alternative beclaimed with a closed transitional phrase such as “consistingessentially of” or “consisting of” whether or not explicitly indicatedthe description portion of the specification.

Additionally, the claims set forth in this specification, if any, arefurther intended to describe the metes and bounds of a limited number ofthe preferred embodiments of the invention and are not to be construedas the broadest embodiment of the invention or a complete listing ofembodiments of the invention that may be claimed. The applicant does notwaive any right to develop further claims based upon the description setforth above as a part of any continuation, division, orcontinuation-in-part, or similar application.

1-35. (canceled)
 36. An atmospheric water harvesting system, comprising:a heat pump having a hot side and a cold side; an adsorption unitcomprising at least one sorbent module containing one or more sorbents,said adsorption unit physically separated from said heat pump; adesorption chamber connected to, or positioned in close proximity to,said hot side of said heat exchanger; a condensation chamberencompassing, or positioned in close proximity to, said cold side ofsaid heat exchanger; and a transfer mechanism configured to: (i)transfer a sorbent module at least partially saturated with water fromsaid adsorption unit into said desorption chamber, and (ii) transfersaid sorbent module at least partially desorbed in said desorptionchamber back to said adsorption unit.
 37. The system of claim 36,wherein said a desorption chamber connected to, or positioned in closeproximity to, said hot side of said heat exchanger transfers heat fromsaid hot side of said heat pump to said sorbent module disposed in saiddesorption chamber to desorb water vapor from said one or more sorbents.38. The system of claim 37, wherein said condensation chamberencompassing, or positioned in close proximity to, said cold side ofsaid heat exchanger to condense water from said desorbed water vaporfrom said one or more sorbents.
 39. The system of claim 37, wherein saiddesorption chamber configured to operate at an average desorptiontemperature.
 40. The system of claim 39, wherein said condensationchamber configured to operate at an average condensation temperature.41. The system of claim 40, wherein said average desorption temperaturemaintains a desorption temperature high enough to sustain a target rateof desorption of water vapor from said one or more sorbents.
 42. Thesystem of claim 41, wherein said system configured to operate at saidaverage desorption temperature and said average condensation temperatureto (i) achieve a lowest energy per liter of water produced with the oneor more sorbents.
 43. The system of claim 41, wherein said systemconfigured to operate at said average desorption temperature and saidaverage condensation temperature to (i) achieve a lowest energy perliter of water produced with the one or more sorbents, and (ii) maintaina desorption temperature high enough to sustain a target rate ofdesorption.
 44. The system of claim 38, further comprising at least onerecirculation fan associated with said desorption chamber to drivedesorption of water vapor from said one or more sorbents resulting in ahigher concentration of water vapor in said desorption chamber.
 45. Thesystem of claim 44, further comprising at least one desorption-condenserrecirculation fan associated with said desorption chamber to (i)transfer hot vapor from said desorption chamber to said condensationchamber, and (ii) recirculate moisture remaining in said condensationchamber back into said desorption chamber.
 46. The system of claim 36,wherein at least one of sorbent module contains at least onemetal-organic framework.
 47. The system of claim 46, wherein said atleast one metal-organic framework has an isotherm step of about 20%relative humidity at about 25° C.
 48. The system of claim 47, whereinsaid system is configured to operate at a desorption temperature ofbetween about 130° C. to about 140° C., and a condensation temperatureof between about 85° C. to about 95° C.
 49. The system of claim 46,wherein said at least one metal-organic framework has an isotherm stepof about 40% relative humidity at about 25° C.
 50. The system of claim49, wherein said system is configured to operate at a desorptiontemperature of between about 115° C. to about 125° C., and acondensation temperature of between about 85° C. to about 95° C.
 51. Thesystem of claim 46, wherein said at least one metal-organic frameworkhas an isotherm step of about 60% relative humidity at about 25° C. 52.The system of claim 51, wherein said system is configured to operate ata desorption temperature of between about 100° C. to about 110° C., anda condensation temperature of between about 85° C. to about 95° C. 53.The system of claim 36, wherein said transfer mechanism comprises arotating carousel or a robotic arm.
 54. The system of claim 36, whereinsaid system further comprises a water collection tank disposed inproximity to said condensation chamber.
 55. The system of claim 36,further comprising a computer coupled to one or more ambient air sensorsor one or more ambient air humidity sensors located outside of saiddesorption chamber, said computer configured to measure ambient airtemperature or ambient air humidity of the environment surrounding thesystem, and combinations thereof.
 56. The system of claim 55, whereinsaid computer further coupled to one or more temperature sensors, or oneor more humidity sensors, or one or more airflow sensors located insidesaid desorption chamber, said computer configured to measure airtemperature, or air humidity, or airflow inside said desorption chamber,or combinations thereof.
 57. The system of claim 56, wherein saidcomputer further coupled to one or more temperature sensors, or one ormore humidity sensors, or one or more airflow sensors located insidesaid condensation chamber, said computer configured to measure airtemperature, or air humidity, or airflow inside said condensationchamber, or combinations thereof.
 58. The system of claim 57, whereinsaid computer further containing a water harvesting algorithm executableto adjust operating parameters of said system based on: i) measurementsof one or more of said air temperature and said air humidity inside saiddesorption chamber and said condensation chamber, and ii) measurementsof one or more of said ambient air temperature and said ambient airhumidity.